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Nickel Alloy Groups

There are many commercially-available, wrought, corrosion-resistant, nickel-based alloys. To understand their characteristics and metallurgy, it is convenient to group them compositionally. The main groups, as defined by alloying elements present at levels of 10 wt.% or above, are as follows:

  1. Commercially-Pure Nickel (Ni)
  2. Nickel-Copper (Ni-Cu)
  3. Nickel-Chromium (Ni-Cr)
  4. Nickel-Molybdenum (Ni-Mo)
  5. Nickel-Chromium-Molybdenum (Ni-Cr-Mo)
  6. Nickel-Chromium-Iron (Ni-Cr-Fe)
  7. Nickel-Iron-Chromium (Ni-Fe-Cr)

The general attributes of each group are listed in the following table, along with the names of some representative alloys:

Group Examples Attributes
C-P Nickel Nickel 200 alloy Very resistant to caustic alkalis. Useful electrical and magnetic properties.
Ni-Cu MONEL® alloy 400 alloy Very resistant to seawater and hydrofluoric acid. Moderately resistant to sulfuric acid. Very resistant to oxidizing acid solutions.
Ni-Cr HASTELLOY® G-35® alloy
Ni-Mo HASTELLOY® B-3® alloy Very resistant to hydrochloric acid and sulfuric acid.
Ni-Cr-Mo HASTELLOY® C-276 alloy Resistant to both oxidizing and reducing acid solutions. Very resistant to chloride-induced pitting, crevice attack and stress corrosion cracking.
Ni-Cr-Fe HASTELLOY® G-30® alloy Very resistant to oxidizing solutions. Moderately resistant to chloride-induced pitting, crevice attack and stress corrosion cracking.
Ni-Fe-Cr INCOLOY® alloy 825 Resistant to oxidizing solutions. Some resistance to sulfuric acid and chloride-induced localized attack.

Compositional details of several materials from each group are given in the table below. For completeness, some casting equivalents are included (although their characteristics are generally affected by microstructural inhomogeneity, and elevated residual element contents).

Group Alloy UNS No. Form Composition wt.% (values denoted with * are maxima, and ** are minima)
- - - - Ni Cu Mo Cr Fe W Mn Si C Al Ti Other
Ni 200 N02200 Wrought 99.5 0.1 - - 0.2 - 0.2 0.2 0.08 - - -
201 N02201 Wrought 99.5 0.1 - - 0.2 - 0.2 0.2 0.01 - - -
301 N03301 Wrought 96.5 0.1 - - 0.3 - 0.2 0.5 0.2 4.4 0.6 -
CZ-100 N02100 Cast 95** 1.25* - - 3* - 1.5* 2* 1* - - -
Ni-Cu 400 N04400 Wrought 66.5 31.5 - - 1.2 - 1 0.2 0.2 - - -
K-500 N05500 Wrought 66.5 29.5 - - 1 - 0.8 0.2 0.1 2.7 0.6 -
M-35-1 N24135 Cast BAL. 29.5 - - 3.5* - 1.5* 1.25* 0.35* - - Nb 0.5
Ni-Mo B-2 N10665 Wrought 69 0.5* 28 1* 2* 0.5* 1* 0.1* 0.01* - - -
B-3® N10675 Wrought 65** 0.2* 28.5 1.5 1.5 3* 3* 0.1* 0.01* 0.5* - -
N-7M N30007 Cast BAL. - 31.5 1* 3* - 1* 1* 0.07* - - -
N-12MV N30012 Cast BAL. - 28 1* 5 - 1* 1* 0.12* - - Co 2.5*, V 0.4
Ni-Cr 600 N06600 Wrought 76 0.2 - 15.5 8 - 0.5 0.2 0.08 - - -
625 N06625 Wrought 61 - 9 21.5 2.5 - 0.2 0.2 0.05 0.2 0.2 Nb + Ta 3.6
690 N06690 Wrought 58** 0.5* - 29 9 - 0.5* 0.5* 0.05* - - -
725 N07725 Wrought 57 - 8 21 7.5 - 0.35* 0.2* 0.03* 0.35* 1.5 Nb 3.5
G-35® N06035 Wrought 58 0.3* 8.1 33.2 2* 0.6* 0.5* 0.6* 0.05* 0.4* - -
ALLCORR N06110 Wrought BAL. - 10 31 - 2 - - 0.02 0.25 0.25 Nb 0.4
Ni-Cr- Mo C-4 N06455 Wrought 65 0.5* 16 16 3* - 1* 0.08* 0.01* - 0.7* -
C-22® N06022 Wrought 56 0.5* 13 22 3 3 0.5* 0.08* 0.01* - - V 0.35*
C-22HS® - Wrought 61 0.5* 17 21 2* 1* 0.8* 0.08* 0.01* 0.5* - -
C-276 N10276 Wrought 57 0.5* 16 16 5 4 1* 0.08* 0.01* - - V 0.35*
C-2000® N06200 Wrought 59 1.6 16 23 3* - 0.5* 0.08* 0.01* 0.5* - -
59 N06059 Wrought BAL. - 16 23 1.5* - 0.5* 0.1* 0.01* 0.25 - -
686 N06686 Wrought BAL. - 16 21 5* 3.7 0.75* 0.08* 0.01* - 0.15 -
CW-2M N26455 Cast BAL. - 16.25 16.25 2* 1* 1* 0.8* 0.02* - - -
CW-6M N30107 Cast BAL. - 18.5 18.5 3* - 1* 1* 0.07* - - -
CW- 12MW N30002 Cast BAL. - 17 16.5 6 4.5 1* 1* 0.12* - - V 0.3
CX-2MW N26022 Cast BAL. - 13.5 21.5 4 3 1* 0.8* 0.02* - - V 0.35*
Ni-Cr-Fe G-3 N06985 Wrought 44 2 7 22 19.5 1.5* 1* 1* 0.015* - - Co 5*, Nb 0.5*
G-30® N06030 Wrought 43 2 5.5 30 15 2.5 1.5* 0.8* 0.03* - - Co 5*, Nb 0.8
G-50® N06950 Wrought 50** 0.5* 9 20 17 1* 1* 1* 0.02* 0.4* Co 2.5*, Nb 0.5*
Ni-Fe-Cr 825 N08825 Wrought 42 2.2 3 21.5 30 - 0.5 0.2 0.05* 0.1 0.9 -
925 N09925 Wrought 44 2.2 3 21 22** - 1* 0.5* 0.03* 0.3 2.2 Nb 0.5*

Cobalt Alloy Groups

There are relatively few wrought, corrosion- and wear-resistant, cobalt-based alloys. On the other hand, there are many cast, wear-resistant, cobalt-based alloys (closely associated with the STELLITE® tradename) that, despite their high carbon contents, possess a modicum of resistance to aqueous corrosion. This manual is concerned with the former materials. However, the cast alloys will be referred to often, since they provide a well-known frame of reference.

There are essentially three types of wrought, cobalt alloys used to resist aqueous corrosion. All contain high levels (20 wt.% or more) of chromium, and significant molybdenum and/or tungsten contents.

First are those derived from the cast, tungsten-bearing, high-carbon alloys, exemplified by HAYNES® 6B alloy (also known as STELLITE® 6B alloy). With a 1 wt.% carbon content, this alloy can be hot worked, but cannot be cold worked. Wrought processing enables the breaking down of large carbide particles (within the cast, ingot structure) into a discontinuous dispersion of equiaxed carbide particles; this results in enhanced ductility, increased resistance to corrosion, and excellent resistance to low stress abrasion, relative to compositionally-similar, cast and weld overlay materials.

Second are those tungsten-bearing, low-carbon, wrought materials designed for high temperature service, but whose resistance to aqueous corrosion is so high that they have found use in low temperature applications also.  The primary example is HAYNES® 25 alloy, which is approved for biomedical use.

Third are those molybdenum-bearing alloys with carbon contents of about 0.35 wt.% or less, and designed to excel in both corrosive solutions and systems subject to wear. The prime example is ULTIMET® alloy, which exhibits a unique blend of properties, including high resistance to aqueous corrosion and wear, relatively high ductility, and excellent weldability.

The nominal compositions of several wrought, corrosion-resistant, cobalt alloys are given in the following table, along with those of several cast, cobalt alloys, for comparison.

Group Alloy UNS No. Form Composition, wt.% (values denoted with * are maxima)
- - - - Co Ni Cr Mo W C Fe Si Mn Other
Tungsten-Bearing 6B R30016 Wrought 58 2.5 30 1.5* 4 1 3* 0.7 1.4 -
1 R30001 Cast BAL 1.5 30 0.5 13 2.5 3* 1.3 0.5 -
W73001** Weld Overlay
6 R30006 Cast BAL 3* 29 1.5* 4.5 1.2 3* 1.5* 1* -
W73006** Weld Overlay
12 R30012 Cast BAL 3* 29.5 1* 8.25 1.5 3* 1.2 1* -
W73012** Weld Overlay
Tungsten-Bearing Low-Carbon 25 R30605 Wrought 51 10 20 1* 15 0.1 3* 0.4* 1.5 -
Molybdenum-Bearing Low-Carbon ULTIMET® R31233 Wrought 54 9 26 5 2 0.06 3 0.3 0.8 -
F75 R30075 Cast BAL 1* 28.5 6 0.2* 0.35* 0.75* 1* 1* Al 0.3*B 0.01*N 0.25*

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